The intrinsic mechanisms of softwood fiber damage in brown stock fiber line unit operations Lappeenranta 2010

The effects of pulp processing on softwood fiber properties strongly influence the properties of wet and dry paper webs. Pulp strength delivery studies have provided observations that much of the strength potential of long fibered pulp is lost during brown stock fiber line operations where the pulp is merely washed and transferred to the subsequent processing stages. The objective of this work was to study the intrinsic mechanisms which maycause fiber damage in the different unit operations of modern softwood brown stock processing. The work was conducted by studying the effects of industrial machinery on pulp properties with some actions of unit operations simulated in laboratory scale devices under controlled conditions. An optical imaging system was created and used to study the orientation of fibers in the internal flows during pulp fluidization in mixers and the passage of fibers through the screen openings during screening. The qualitative changes in fibers were evaluated with existing and standardized techniques. The results showed that each process stage has its characteristic effects on fiber properties: Pulp washing and mat formation in displacement washers introduced fiber deformations especially if the fibers entering the stage were intact, but it did not decrease the pulp strength properties. However, storage chests and pulp transfer after displacement washers contributed to strength deterioration. Pulp screening proved to be quite gentle, having the potential of slightly evening out fiber deformations from very deformed pulps and vice versa inflicting a marginal increase in the deformation indices if the fibers were previously intact. Pulp mixing in fluidizing industrial mixers did not have detrimental effects on pulp strength and had the potential of slightly evening out the deformations, provided that the intensity of fluidization was high enough to allow fiber orientation with the flow and that the time of mixing was short. The chemical and mechanical actions of oxygen delignification had two distinct effects on pulp properties: chemical treatment clearly reduced pulp strength with and without mechanical treatment, and the mechanical actions of process machinery introduced more conformability to pulp fibers, but did not clearly contribute to a further decrease in pulp strength. The chemical composition of fibers entering the oxygen stage was also found to affect the susceptibility of fibers to damage during oxygen delignification. Fibers with the smallest content of xylan were found to be more prone to irreversibledeformations accompanied with a lower tensile strength of the pulp. Fibers poor in glucomannan exhibited a lower fiber strength while wet after oxygen delignification as compared to the reference pulp. Pulps with the smallest lignin content on the other hand exhibited improved strength properties as compared to the references.

Central African identities and religiosity in colonial Minas Gerais

This study deals with the import of West Central African slaves and their religious practices to Minas Gerais in the eighteenth century. The captaincy of Minas Gerais in the interior of Brazil developed into the world’s largest gold producing region in the beginning of the eighteenth century. The large-scale mining of gold, and later diamonds, was only possible through massive imports of slaves from Africa to Brazil. The first part of this study discusses the Atlantic slave trade in the southern Atlantic world. The discovery of gold in Minas Gerais led to an increasing demand for slaves in Brazil, which was largely met by supplies from Angola. The study analyzes the formation of Central Africans’ identities both in their homelands and in Brazil. Slave identities or “nations” have often been seen as creations of the slave owners. By interpreting major Central African “nations” such as Angola, Congo, and Benguela as regional identities that were tied to the slaves’ origins in Africa, this study offers a new interpretation of what these identities meant for Central Africans in Minas Gerais. The second part of this study concentrates on the religious universe of Central Africans. Processes of cultural creolization affected West Central African societies after the Portuguese landed in the kingdom of Kongo in the late fifteenth century and led to the development of an Atlantic Creole culture. The spread of Catholicism in West Central Africa affected religious life especially in the kingdom of Kongo, in the city of Luanda, and in the Portuguese colony of Angola. Central African religious specialists were often denounced to the authorities in Angola for organizing healing and divination rituals. Diagnosis in these rituals was often made through spirit possession. Central Africans took these healing and divining methods to Minas Gerais, where numerous African religious specialists enjoyed great prominence. In the Brazilian mining region, it was commonplace that African healers served not only the African slave population, but also free whites. In the eighteenth century, Central African popular healers made a significant contribution to the therapeutic arts practiced in Minas Gerais and elsewhere in Brazil.